The ARMv8.4-PMU extension adds:
 * one new required event, STALL
 * one new system register PMMIR_EL1

(There are also some more L1-cache related events, but since
we don't implement any cache we don't provide these, in the
same way we don't provide the base-PMUv3 cache events.)

The STALL event "counts every attributable cycle on which no
attributable instruction or operation was sent for execution on this
PE".  QEMU doesn't stall in this sense, so this is another
always-reads-zero event.

The PMMIR_EL1 register is a read-only register providing
implementation-specific information about the PMU; currently it has
only one field, SLOTS, which defines behaviour of the STALL_SLOT PMU
event.  Since QEMU doesn't implement the STALL_SLOT event, we can
validly make the register read zero.

Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
 target/arm/cpu.h    | 18 ++++++++++++++++++
 target/arm/helper.c | 22 +++++++++++++++++++++-
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index e043932fcb1..cfa9fd6c1b9 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -3519,6 +3519,13 @@ static inline bool isar_feature_aa32_pmu_8_1(const 
ARMISARegisters *id)
         FIELD_EX32(id->id_dfr0, ID_DFR0, PERFMON) != 0xf;
 }
 
+static inline bool isar_feature_aa32_pmu_8_4(const ARMISARegisters *id)
+{
+    /* 0xf means "non-standard IMPDEF PMU" */
+    return FIELD_EX32(id->id_dfr0, ID_DFR0, PERFMON) >= 5 &&
+        FIELD_EX32(id->id_dfr0, ID_DFR0, PERFMON) != 0xf;
+}
+
 /*
  * 64-bit feature tests via id registers.
  */
@@ -3704,6 +3711,12 @@ static inline bool isar_feature_aa64_pmu_8_1(const 
ARMISARegisters *id)
         FIELD_EX64(id->id_aa64dfr0, ID_AA64DFR0, PMUVER) != 0xf;
 }
 
+static inline bool isar_feature_aa64_pmu_8_4(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_aa64dfr0, ID_AA64DFR0, PMUVER) >= 5 &&
+        FIELD_EX32(id->id_aa64dfr0, ID_AA64DFR0, PMUVER) != 0xf;
+}
+
 /*
  * Feature tests for "does this exist in either 32-bit or 64-bit?"
  */
@@ -3722,6 +3735,11 @@ static inline bool isar_feature_any_pmu_8_1(const 
ARMISARegisters *id)
     return isar_feature_aa64_pmu_8_1(id) || isar_feature_aa32_pmu_8_1(id);
 }
 
+static inline bool isar_feature_any_pmu_8_4(const ARMISARegisters *id)
+{
+    return isar_feature_aa64_pmu_8_4(id) || isar_feature_aa32_pmu_8_4(id);
+}
+
 /*
  * Forward to the above feature tests given an ARMCPU pointer.
  */
diff --git a/target/arm/helper.c b/target/arm/helper.c
index aeb01617150..2feded1518c 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1130,6 +1130,12 @@ static bool pmu_8_1_events_supported(CPUARMState *env)
     return cpu_isar_feature(any_pmu_8_1, env_archcpu(env));
 }
 
+static bool pmu_8_4_events_supported(CPUARMState *env)
+{
+    /* For events which are supported in any v8.1 PMU */
+    return cpu_isar_feature(any_pmu_8_4, env_archcpu(env));
+}
+
 static uint64_t zero_event_get_count(CPUARMState *env)
 {
     /* For events which on QEMU never fire, so their count is always zero */
@@ -1170,6 +1176,11 @@ static const pm_event pm_events[] = {
       .get_count = zero_event_get_count,
       .ns_per_count = zero_event_ns_per,
     },
+    { .number = 0x03c, /* STALL */
+      .supported = pmu_8_4_events_supported,
+      .get_count = zero_event_get_count,
+      .ns_per_count = zero_event_ns_per,
+    },
 };
 
 /*
@@ -1178,7 +1189,7 @@ static const pm_event pm_events[] = {
  * should first be updated to something sparse instead of the current
  * supported_event_map[] array.
  */
-#define MAX_EVENT_ID 0x24
+#define MAX_EVENT_ID 0x3c
 #define UNSUPPORTED_EVENT UINT16_MAX
 static uint16_t supported_event_map[MAX_EVENT_ID + 1];
 
@@ -6414,6 +6425,15 @@ static void define_pmu_regs(ARMCPU *cpu)
         };
         define_arm_cp_regs(cpu, v81_pmu_regs);
     }
+    if (cpu_isar_feature(any_pmu_8_4, cpu)) {
+        static const ARMCPRegInfo v84_pmmir = {
+            .name = "PMMIR_EL1", .state = ARM_CP_STATE_BOTH,
+            .opc0 = 3, .opc1 = 0, .crn = 9, .crm = 14, .opc2 = 6,
+            .access = PL1_R, .accessfn = pmreg_access, .type = ARM_CP_CONST,
+            .resetvalue = 0
+        };
+        define_one_arm_cp_reg(cpu, &v84_pmmir);
+    }
 }
 
 /* We don't know until after realize whether there's a GICv3
-- 
2.20.1


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